Mr. Jeffreys on the Animal of Stilifer Turtoni. 333 



spawn, which appeared to be in various stages of development. 

 The adult Stilifers were not firmly attached to the Echinus (like 

 the Caligus to a codfish), but frequently shifted their places by 

 creeping between the spines. I gently removed one of them 

 with a stiff camel's-hair brush, and placed it in a glass tube with 

 sea-water. It was at first very sluggish or timid, and evidently 

 unaccustomed to its new habitat, lying at the bottom of the 

 tube; but afterwards it recovered itself, and crawled up the 

 side by means of the front part of its foot, very slowly and by 

 an imperceptible movement ; the other part of the foot was not 

 pressed to the glass, but rested on the mantle. The foot was 

 occasionally twisted about and contracted, as if through uneasi- 

 ness. The animal was never wholly withdrawn into the shell, 

 although I irritated it with that object. The sUt in the foot 

 probably serves for the admission of water into some tubular 

 cavity or vessels which permeate this organ : this would have 

 the effect of enlarging and swelling the foot, so as to protect the 

 Stilifer from being crushed by the spines of tbeEchinus. A slight 

 leverage or action of this kind at the base of the spines would, 

 of course, answer the purpose far better than a much stronger 

 leverage or power exerted at the top of the spines. The fry are 

 enveloped in a gelatinous case. When detached and examined 

 under a microscope, each had three lobes, of which the two 

 larger were in front ; these were finely ciliated, the cilia being 

 rather long, and their points sometimes touching the surface of 

 the glass cell which contained the fry. The fry rapidly whirled 

 themselves about by means of the cilia, but occasionally rested. 

 They occupied nautiloid shells of a single turn. 



One of the Stilifers appeared to be full of spawn-masses, 

 which were perceptible with the microscope by reason of the 

 shell being transparent. The other Stilifer was a male. I after- 

 wards replaced the latter in its old quarters, where it was evi- 

 dently more comfortable than in the glass tube ; and it soon 

 adhered to the sea-egg by the prehensile lobe of its foot, and 

 settled down among the spines. 



The ciliation of the body in Stilifer is also a characteristic 

 feature of Homalugyra (perhaps the living representative of 

 Euomphalus), which is a minute (but not microscopical) mollusk, 

 without tentacles, and forms a discoidal shell. It is an inhabit- 

 ant of the European seas, and comprises two species. Forbes and 

 Hanley called one of these species Skenea nitidissima, and the 

 other Skenea Rota. Dr. Fischer imagined that the first-named 

 species was the fry of some larger mollusk, because it was ci- 

 liated ; but he must have either overlooked the fact, or else not 

 have been aware, that in all the species of Trochus, Rissoa, and 



